Chapter 13: Troubleshooting network connectivity

Unit objectives• Identify TCP/IP troubleshooting tools • Discuss the Telnet utility and its functions• Discuss the functions the File Transfer

Protocol (FTP) utility • Diagnose a problem and choose the

appropriate troubleshooting tools

Topic A

• Topic A: TCP/IP troubleshooting tools • Topic B: Telnet • Topic C: File Transfer Protocol • Topic D: Troubleshooting examples

TCP/IP troubleshooting tools • ARP • HOSTNAME • IPCONFIG • WINIPCFG • IFCONFIG• NBTSTAT • NETSTAT • NSLOOKUP • PING • TRACERT • ROUTE

ARP (and RARP) • ARP supports All TCP/IP clients• Helps a host to find

– the MAC address of another host – on the same internetwork, – if appropriate host’s IP address is given

• RARP is used to find a host’s own IP address, when it’s own MAC address is known.– For a “network boot”.

TCP/IP Utilities

• Ping• Traceroute or tracert• Arp• Netstat• Nbtstat (NetBIOS names)• Many more….

Ping

pinging

Tracert

Arp protocol Short for Address Resolution Protocol, a TCP/IP

protocol used to convert an IP address into a physical address, such as an Ethernet address. A host wishing to obtain a physical address broadcasts an ARP request onto the TCP/IP network.

The host on the network that has the IP address in the request then replies with its physical hardware address.

There is also Reverse ARP (RARP) which can be used by a host to discover its IP address. In this case, the host broadcasts its physical address and a RARP server replies with the host's IP address.

Webopedia.com

Arp functions

Arp

Netstat functions

Netstat –r

Netstat –n

Netstat –a

Netstat -e

Nbtstat (NetBIOS over TCP/IP) Functions http://www.zdnet.co.uk/news/specials/2000/10/enterprise/techrepublic/2002/02/article002.html

HOSTNAME

• Supports All TCP/IP clients• Used to determine the local machine’s host name• Just type “hostname” from a command prompt

IPCONFIG

• Supports Windows 98 and Windows NT/2000/Server 2003/XP platforms

• Displays the current IP settings for the system• Used to renew or release IP addresses

assigned by a DHCP server

WINIPCFG

• Supports Windows 95 and Windows 98 platforms

• Helps to obtain information about the system’s TCP/IP configuration

WINIPCFG

Activity A-1 page 13-6\begin on Monday, 12-1

Discussing ARP, HOSTNAME, IPCONFIG, and WINIPCFG

IFCONFIG

• Supports UNIX platform• Displays the current network interface setting

for the system

NBTSTAT

• Supports Windows 95/98 and Windows NT/2000/Server 2003/XP platforms

• Helps to view and NetBIOS name cache information manage

NETSTAT

• Supports all TCP/IP clients • Displays protocol statistics and current

TCP/IP network connections

NETSTAT – an example

Another Example, my own PC• C:\Documents and Settings\Administrator.NETVISTA> • TCP netvista:27015 localhost:3636 ESTABLISHED• TCP netvista:3846 a96-17-73-43.deploy.akamaitechnologies.com:http CLOSE_WAIT• TCP netvista:3848 a96-17-171-147.deploy.akamaitechnologies.com:http CLOSE_WAIT• TCP netvista:3849 a96-17-72-98.deploy.akamaitechnologies.com:http CLOSE_WAIT• TCP netvista:3850 a96-17-171-147.deploy.akamaitechnologies.com:http CLOSE_WAIT• TCP netvista:4835 an-in-f19.google.com:http ESTABLISHED• TCP netvista:4852 static-209-18-39-90.nyc20.tbone.rr.com:http ESTABLISHED• TCP netvista:4853 a96-17-75-145.deploy.akamaitechnologies.com:http ESTABLISHED• TCP netvista:4854 static-209-18-39-90.nyc20.tbone.rr.com:http ESTABLISHED• TCP netvista:4859 carepages.com.102.112.2o7.net:https TIME_WAIT• TCP netvista:4861 a96-17-75-162.deploy.akamaitechnologies.com:http ESTABLISHED• TCP netvista:4863 a96-17-74-90.deploy.akamaitechnologies.com:https ESTABLISHED• TCP netvista:4879 205-177-69-58.btnaccess.net:http ESTABLISHED• TCP netvista:4889 carepages.com.102.112.2o7.net:https TIME_WAIT• TCP netvista:4898 yx-in-f18.google.com:http ESTABLISHED• TCP netvista:4899 yx-in-f18.google.com:http ESTABLISHED

Activity A-2 page 13-9

Discussing IFCONFIG, NBTSTAT, and NETSTAT

NSLOOKUP

• Supports all TCP/IP clients • Retrieves information stored by the DNS

server• Is an industry standard used for obtaining

information from a DNS server

DIG

• Used to support only UNIX clients, but has now been ported to the Windows platform as well

• Lets you retrieve information stored by the DNS server

• Doesn’t come with Windows • Neither NSLOOKUP nor DIG will work with a

workgroup; you have to be in a domain.• Both NSLOOKUP and DIG examine the DNS server

search process.

DIG – an example

PING

• Supports all TCP/IP clients • Verifies connections to one or more remote

computers

TRACERT

• Supports all TCP/IP clients • Used to trace the route that a packet takes to

reach the destination

TRACERT – an example

ROUTE

• Supports all TCP/IP clients • Used to manage static routing tables

Activity A-3 page 13-15

Discussing NSLOOKUP, DIG, TRACERT, PING, and ROUTE

Topic B

• Topic A: TCP/IP troubleshooting tools • Topic B: Telnet • Topic C: File Transfer Protocol • Topic D: Troubleshooting examples

Telnet

• Supports dumb terminal connection and emulation with remote servers

• Telnet provides access through terminal emulation to any host running a Telnet daemon service

• Used for remote configuration of hubs and routers

Telnet utility on Windows NT/2000/XP/Server 2003

• When TCP/IP is installed on a Windows NT/2000/XP/Server 2003 station, Telnet is added to the system

Troubleshooting with Telnet

• Telnet is a powerful diagnostic tool • It provides a way of sending commands

directly to a server process and viewing the results when higher-level protocols or applications appear to be failing

Activity B-1 page 13-17

Discussing Telnet

Topic C

• Topic A: TCP/IP troubleshooting tools • Topic B: Telnet • Topic C: File Transfer Protocol • Topic D: Troubleshooting examples

File Transfer Protocol

• File Transfer Protocol (FTP) transfers text and binary files between systems, including dissimilar platforms

• Performs a format and type conversion on the file

• Supports all TCP/IP clients• Can be used interactively at the command

prompt or in a script (batch) file

FTP commands

• help [command] • quit or bye • ascii • binary • get • put

Activity C-1 page 13-19

Discussing File Transfer Protocol

Topic D

• Topic A: TCP/IP troubleshooting tools • Topic B: Telnet • Topic C: File Transfer Protocol • Topic D: Troubleshooting examples

Troubleshooting examples

• TCP/IP suite of utilities can be used to troubleshoot: – Routers– E-mail system– MAC address– Overlapping scopes

Activity D-1

Troubleshooting sample problems

Unit summary

• Identified TCP/IP troubleshooting tools • Discussed the Telnet utility and its functions• Discussed the functions the File Transfer

Protocol (FTP) utility • Learned to diagnose a problem and choose

the appropriate troubleshooting tools